Essentials: The Neuroscience of Speech, Language & Music | Dr. Erich Jarvis

[00:02] where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman and I'm a professor of neurobiology and ophthalmology at

[00:15] Stanford School of Medicine. And now, for my discussion with Dr. Eric Jarvis. >> Thank you. >> Yeah. Very interested in learning from you about speech and language. In terms of the study of speech and language and

[00:30] thinking about how the brain organizes speech and language, uh what are the language? >> There really isn't such a sharp distinction. Now, let me tell you how some people think of it now. That

[00:45] there's a separate language module in the brain that has all the algorithms and computations that influence the speech pathway on how to produce sound and the auditory pathway on how to perceive and interpret it uh for speech

[01:00] or for, you know, sound that we call speech. I don't think there is any good evidence for a separate language module. Instead, there is a speech production pathway that's controlling our larynx,

[01:13] controlling our jaw muscles, that has built within it all the complex algorithms for spoken language. And there's the auditory pathway that has built within it all the complex algorithms for understanding speech, not

[01:28] separate from a language module. And the speech production pathway is specialized to humans and parrots and songbirds, whereas this auditory perception pathway is more ubiquitous amongst the animal kingdom.

[01:42] And this is why dogs can understand sit, sientese, come here ball boy, get the ball, and so forth. Dogs can understand several hundred human speech words. Great apes, you can teach them for several thousand, but they can't say a

[01:57] >> What do we understand about modes of communication that are like language, but might not be what would classically be called language? >> So, next to the brain regions that are controlling spoken language are the

[02:11] hands. And that hand parallel pathway has also complex algorithms that we can utilize. And some species are more advanced in these circuits, whether it's sound or gesturing with hands, and some are less

[02:27] Humans are the most advanced at spoken language, but not necessarily as big a difference at gestural language compared to some other species. So, as you and I are talking here today, and people who are

[02:41] listening but can't see us, we're actually gesturing with our hands as we talk uh without knowing it, or doing it unconsciously. And if we were talking on a telephone, I would have one hand here and I'd be gesturing with the other hand

[02:55] uh without even you seeing me, right? And so, why is that? Uh some have argued, and I would agree with based upon what we've seen, is that there's an evolutionary relationship between the brain pathways that control speech

[03:08] production and gesturing. Uh and and the brain regions I mentioned why is that? I think that the brain pathways that control speech evolved out movement. All right? And um

[03:25] that uh when you talk about Italian, French, English, and so forth, um each one of those languages come with a learned set of gestures that uh you can communicate with. Now,

[03:38] how is that related to other animals? Well, Koko, a gorilla who was raised with humans for 39 years or more, uh learned how to do gesture communication. Learned how to sign

[03:50] language, so to speak, right? But Koko couldn't produce those sounds. Koko could understand them as well by sign by seeing somebody sign or hearing somebody produce speech, but Koko couldn't produce it with her voice.

[04:06] And so what's going on there is that a number of species, not all of them, a number of species have motor pathways in the brain where you can do learned gesturing, rudimentary language if you wanted to say with your limbs, even if

[04:20] it's not as advanced as humans, but they don't have this extra brain pathway for the sound. So they can't gesture with their voice in the way that they gesture >> One thing that I've wondered about for a very long time is whether or not

[04:35] primitive emotions and primitive sounds are the early substrate of language. When I smell something delicious, I typically inhale

[04:47] more and I might say or something like that. Whereas if I smell something putrid, I typically turn away, I wince, and I will exhale trying to not ingest those molecules or inhale those molecules. I could imagine that

[05:02] these are the basic dark and light contrasts of the language system. Is this kind of primitive to more sophisticated pyramid of of sound to language? Is this a crazy idea? Do we have any

[05:16] it works? >> No, it's not a crazy idea and in fact you hit upon one of the key distinctions in the field of research that I had research. Most vertebrate species vocalize, but most of them are producing

[05:32] innate sounds that they're born with, that is babies crying, for example, or dogs barking. And only a few species have learned vocal communication, the ability to imitate sounds. And that's is what makes spoken language special. When

[05:48] people think of what's special about language, it's the learned vocalizations. That is what's rare. So, all the things you talked about, the breathing, the grunting, and so forth, a lot of that is handled by the brainstem

[06:00] circuits, you know, right around the level of your neck and below. Uh like a reflex kind of thing. So, or or behavior in the hypothalamus and so forth.

[06:13] But, for a learned behavior, learning how to speak, uh learning how to play the piano, teaching a dog to learn how to do tricks, is using the forebrain circuits. And what has happened is that there's a

[06:27] controlling learning how to move body parts in these species, but not for the vocalizations. But, in humans and in parrots and some other species, somehow we acquired circuits where the forebrain has taken over the brainstem,

[06:42] and now using that brainstem not only to produce the innate behaviors or vocal behaviors, but the learned ones as well. >> Do we have any sense of when evolved?

[06:56] belong to, we are the only ones that have this advanced vocal learning Uh Now, sapiens. Uh then you can go back in time now

[07:11] based upon genomic data not only of us living humans, but of the fossils that have been found for Homo sapiens, of Neanderthals, of Denisovan sapiens, of Neanderthals, of Denisovan uh individuals, and discover that our

[07:25] uh individuals, and discover that our ancestor our human ancestors supposedly hybridized with these other hominid species. And it was assumed that these other hominid species don't learn how to

[07:37] imitate sounds. I don't know of any species today that's that can have children with a non-vocal learning species. didn't exist. Uh and when we look at the genetic data

[07:51] Uh and when we look at the genetic data from these ancestral hominids that uh you know, where we can look at genes that are involved in learn vocal communication, they have the same sequence as we humans do

[08:03] circuits. So, I think Neanderthals had spoken advanced as what it is in humans, I don't know. Um but I think it's been there for at least between 500,000 to a million

[08:16] >> Maybe we could talk a little bit more about the overlap between brain circuits that control language and speech in humans and other animals. You know, I was weaned in the neuroscience era where bird song and the uh

[08:31] the ability of birds to learn their tutor song was and still is a prominent field and um subfield of neuroscience. And this notion of a critical period, a time in which language is learned more easily than it is later in life. And

[08:45] the names of the different brain areas were quite different. Um it when one opens the textbooks, we hear Wernicke's and Broca's for the humans and then you >> HVC >> Yeah, a robust archistriatum, area X,

[08:59] >> how similar or different are the brains uh brain areas controlling speech and language in say a songbird and a and a young human child? >> Yeah. So, going back to the 1950s or and even a little earlier and Peter Marler

[09:13] and others who got involved in neuroethology, the study of neurobiology of behavior in a natural way, right? Um you know, they started to find that there are these species of birds like songbirds and parrots and now we also

[09:29] know hummingbirds, just three of them out of the 40-something bird groups out there on the planet, orders, that they can imitate sounds like we words, they had this kind of behavior that's more similar to us than

[09:43] chimpanzees have with us or than chickens have with them, right? They're more closer relatives. And then they discovered even more similarities, these critical periods that if you remove a child you know, this unfortunately

[09:56] happens where a child is feral and is not raised with human and goes through their puberty phase of growth becomes hard for them learn a language as an adult. So there's this critical period where you learn best. And even

[10:09] later on when you're in regular society, it's hard to learn. Well, the same birds undergo these same thing. And then it was discovered that if they become deaf, we humans become deaf, our speech starts to deteriorate without any kind of

[10:23] therapy. Uh if a non-human primate or um you know, or let's say a chicken becomes deaf, uh their vocalizations don't deteriorate, very little at least. Uh well, this happens in the vocal

[10:37] learning birds. So there were all these behavioral parallels that it came along with a package. And then people looked into the brain, Fernando Nottebohm, my former PhD advisor, and began to discover the area X you talked about, uh

[10:50] the robust nucleus of the arcopallium. And um in the species who couldn't imitate. So there was a parallel here. And then uh jumping many years later, you know, I started to dig down into

[11:05] these uh brain circuits to discover that these brain circuits had parallel functions with the brain circuits for humans, even though they're by a different name like Broca's and laryngeal motor cortex. And most

[11:17] actual circuitry and the connectivity are similar, but the underlying genes that are expressed in these brain from the rest of the brain are also similar between humans and songbirds and

[11:31] parrots. So all the way down to the genes and now we're finding the specific are also similar. Not always identical, but similar. Uh which indicates remarkable convergence for a so-called complex

[11:43] behavior in species separated by 300 million years from a common ancestor. that mutations in these genes that cause speech deficits in humans like in FOXP2,

[11:58] uh if you put those same mutations or similar type of deficits in these vocal learning birds, you get similar deficits. So, convergence of the behavior is associated with similar genetic disorders of the behavior.

[12:11] >> Do hummingbirds sing or do they hum? >> Hummingbirds hum with their wings and >> In a coordinated way? >> In a coordinated way. There is some species of hummingbirds um that actually will

[12:25] um Doug Archler showed this that will flap uh their wings and create a slapping sound with their wings that's in unison with their song. And oh and like a particular syllable in their songs uh even though it's their wings

[12:43] and their voice at the same time. >> Hummingbirds are clapping to their song. >> Clapping with their they're snapping their wings together uh in unison with a song to to make it like if I'm going ba da da da da ba da.

[12:56] You know, I banged on the table. Except they make it almost sound like their voice with their wings. What's amazing about hummingbirds and I we're going to say vocal learning species in general is that for whatever reason, they seem to

[13:09] evolve multiple complex traits. You know, this idea that the evolving language, spoken language in particular, comes along with a set of specializations. >> When I was coming up in neuroscience, I

[13:24] learned that I think it was the work of Peter Marler that um young birds learn songbirds learn their tutor's song and learn it quite quite well, but that

[13:36] tutor. In other words, they could learn a different and for the listeners I'm language, a different bird song, different than their own species song, but never as well as they could learn their own natural

[13:51] >> Yes. >> Genetically linked meaning that it would be like me being raised in a different culture and um language, but not as well as I would have learned English. This this is the

[14:05] >> That is true. Yes, and that's and that's and and talked to Peter Marler himself about before he passed. Um yeah, this he used to call it the innate predisposition to learn. All right, so

[14:19] um which would be kind of the equivalent in the linguistic community of universal grammar. There is something genetically influencing our vocal communication on top of what

[14:33] we learn culturally. And so there is this balance between the genetic control of speech or a song in these birds and the learned uh cultural control. And so the learned uh cultural control. And so so yes, if you were to take um you know,

[14:48] um I mean in this case we we actually tried this at Rockefeller later on, take a zebra finch and raise it with a canary, it would sing a song that was sort of like a hybrid in between. We call it a caninch. Right?

[15:02] Uh and vice versa for the canary because there's something different about their vocal musculature or the or the circuitry in the brain. And with a zebra finch, even with a closely related species, if you would take a zebra finch

[15:15] uh young animal and in one cage next to it place its own species adult male, right? And in the other cage place a Bengali finch next to it, it would preferably learn the song from the its own species neighbor. But if you remove

[15:30] its neighbor, it would learn that Bengali finch very well. >> So, there's it it has something to do with also the social bonding with your >> That raises a question that I've based on something I also heard, but I don't

[15:43] have any scientific peer-reviewed publication to point to, which is this this idea of pigeon, not the bird, but this idea of when multiple cultures and area that the children of all the different native languages will come up

[15:58] with their own language. I think this was in island culture, maybe in Hawaii, called pigeon, which is sort of a hybrid of the various languages that their parents speak at home and that they themselves speak, and

[16:11] that somehow pigeon, again, not the bird, but a language called pigeon for reasons I don't know, harbors certain basic elements of all true? >> What is going on here is

[16:27] cultural evolution remarkably tracks genetic evolution. So, if you bring together that have been in in their separate populations evolutionarily at

[16:39] least for hundreds of generations. So, someone speaking Chinese, someone uh and that child uh then's learning from both of them. Yes, that child's going to be able to pick up and merge uh uh uh phonemes and

[16:56] words together in a way that an adult wouldn't because why? They're experiencing both languages at the same time during their critical period uh years in a way that um adults would not be able to experience. And so, you get a

[17:11] And the lowest common denominator is going to be what they share. And so, the phonemes that they retained in each of their imagine, used the most. >> So we've got

[17:26] brain circuits in songbirds and in humans that in many ways are similar, perhaps not in their exact wiring, but in their basic contour of wiring, and genes that are expressed in both sets of neural circuits in very distinct species

[17:40] that are responsible for these phenomena we're calling speech and language. I >> Uh one of the things that differ in the pathways of birds is some of the connections are fundamentally different

[17:53] than the surrounding circuits. Like a a direct cortical connection vocalizations in the cortex to the motor neurons that control the larynx in humans or the syrinx in birds. And so we actually made a prediction

[18:08] that since some of these connections differ, we're going to find genes that that control neuroconnectivity and that specialize in that differ. And that's exactly what we found. Uh genes that control what we call axon

[18:22] guidance and formation of connections. And what was interesting, it was sort of in the opposite direction that we expected. That is some of these genes, actually a number of them that control neuroconnectivity

[18:34] in the speech circuit. All right. Uh and it didn't make sense to us at first until we started to realize the function of these genes are to repel connections from forming. So repulsive molecules. And so when you

[18:48] connections to form that normally would have not formed. So it's So by turning it off, you got a gain of function for speech, right? Um other genes that surprised us were genes involved in

[19:02] calcium buffering, neuroprotection. Like a parvalbumin or heat shock protein. So when your brain gets hot, these proteins turn on. And we couldn't the case? And then the idea popped to me one day.

[19:16] I said, "Ah, when I heard the larynx is the fastest firing muscles in the body." All right? In order to vibrate sound and and modulate sound in the way we do, you have to control you have to move those muscles, you know, three to four to five

[19:33] or running. And so, um brain areas that control learn vocalizations in these birds, and I think in humans as well, uh those neurons are firing at a higher rate to

[19:48] control these muscles. And so, what is that going to do? You're going to have lots of toxicity in those neurons unless you upregulate molecules take out uh the extra load that is needed to

[20:00] control the larynx. And then finally, a third set of genes that are uh specialized in these speech circuit are involved in neuroplasticity. Uh neuroplasticity meaning allowing the brain circuits to be more flexible, uh

[20:15] so you can learn better. And why is that? I think learning how to produce that? I think learning how to produce speech is a more complex learning ability than say learning how to walk or or learning how to do tricks and

[20:28] jumps and so forth that dogs do. >> In terms of plasticity of speech and the ability to learn multiple languages, but even just one language, what's going on then the second question is, if one can already speak more than one language as

[20:44] a consequence of childhood learning, is it easier to acquire new languages later >> Actually, the entire brain uh is undergoing a critical period development, not just the speech pathways. And uh so, it's easier to

[20:57] learn how to play a piano. It's easier to learn how to ride a bike for the first time and so forth as a young child than it is later in life. The brain can only hold so much information, and if you are undergoing rapid learning to

[21:13] learn to acquire new knowledge, you also have to put memory or information in in the trash, like in a computer. You You only have so many gigabases of memory. Plus also for survival, you don't want to keep forgetting things.

[21:26] And so So, the brain is designed, I believe, to undergo this critical period and solidify the circuits with what you learned as a child, and you use that for the rest of your life. And now, the

[21:39] question you asked about if you learned more languages as a child, can you Is it easier to learn as an adult? And that's a common uh finding out there in the against it, but for those that support it, the idea there is

[21:54] um you you are born with a set of innate sounds you can produce of phonemes, and you narrow that down, because not all languages use all of them. And so, you narrow down the ones you use to string the phonemes together in words

[22:07] that you learn, and you maintain those phonemes as an adult. And here comes along another language that's using those phonemes or in the in different combinations you're not used to, uh and therefore, you it's like starting from

[22:20] first principles. But if you already have them in multiple languages that you're using, then it makes it easier to use them in another third or fourth language. So, it's not like your brain has under has maintained greater

[22:32] plasticity, is your your brain has maintained greater ability to produce different sounds that then allows you to learn another language faster. >> What about modes of speech and language that seem to have a depth of

[22:45] emotionality and meaning, but for which it departs from structured language? I think of musicians, like there's some Bob Dylan songs that to me I understand the individual words. I like to think there's an emotion

[23:00] experience some sort of emotion and I have a guess about what he was experiencing. But if I were to just read it linearly without the music and without him singing it or somebody singing it like him, it wouldn't hold

[23:14] any meaning. So in other words, uh words that seem to have meaning but not associated with language but somehow tap into an emotionality. >> Absolutely. So So we call this difference um semantic communication,

[23:29] communication with meaning, and effective communication, that has more of an emotional feeling content to it. I believe, you know, based upon imaging work and work we see in birds, when when birds are

[23:44] their sounds, which is not too often, but it happens, versus uh effective communication, sing because I'm trying to attract the mate, my courtship song, or defend my territory. It's the same brain circuits. It's the same

[23:58] speech-like or song circuits are being used in different ways. There's several for for the those listening out there to hear is that when I say also this hear is that when I say also this effective and um semantic communication

[24:13] um being used by similar brain circuits, it also matters the side of the brain. Uh in birds and in humans, um there's there's left-right dominance uh for learned uh communication, learned sound communication. Uh so the left in

[24:29] us humans is more dominant for speech. But the right has a more balance for singing or processing musical sounds as opposed to processing speech. Both get used for both reasons. And so when people say your right brain is your

[24:45] artistic brain and your left brain is your thinking brain, this is what they're referring to. Uh and uh so that's another distinction. The second uh uh thing that's useful to know is that all vocal learning species use

[24:59] their learned sounds for this emotional effective kind of communication. But only a few of them, like humans and some parrots and dolphins, use it for calling speech. And and that has led a number of people

[25:16] to hypothesize that the evolution of spoken language of speech evolved first spoken language of speech evolved first for singing. Uh for this more like emotional kind of mate attraction, like the Jennifer Lopez, the Ricky Martin

[25:30] kind of songs and so forth. Uh and then later on it became used for abstract communication like we're doing now. >> I'd love to chat a moment about facial expression, many of which are subconscious. We are all familiar with

[25:44] the fact that when what somebody says doesn't match some specific feature of their facial expression, that it can um call, you know, that mismatch can cue >> Yeah. >> So, how does motor circuitry that

[25:58] controls facial expression map onto the the brain circuits that control hand movements? >> Yeah. And you ask a great question because we both know some colleagues like Win McFall at Rockefeller

[26:11] University who study facial expression and the neurology behind it. Non-human primates have a lot of diversity in their facial expression like we humans do. And what we know about the neurobiology

[26:23] muscles of the face some other species that don't learn how to imitate vocalizations, they have strong connections from the cortical regions to the motor neurons that

[26:38] though it's more diverse in these non-human primates, there was already a pre-existing diversity of communication, whether it's intentional or unconscious, through facial expression in our land And on top of that, we humans now add

[26:55] the voice uh along with those facial expressions. You're emailing, and someone says something by email, someone can interpret that angrily or or gently, uh

[27:08] and it it bec- becomes ambiguous. The facial expressions get rid of that >> I'm so glad you brought that out because my next question was and is about written language. What is the process of going from a thought to language to

[27:23] written word? And what's going on there? What do we know about the neural >> What I think is going on is, to explain what you're asking, is about perspective reading something. You read something on a paper,

[27:38] your eyes, it goes to the back of your brain to your visual cortical regions, eventually. That visual signal then goes to your speech pathway in the motor cortex in front of you in Broca's area, and you silently speak what you read in

[27:54] your brain without moving your muscles. And sometimes, actually, if you put electrodes EMG electrodes on your laryngeal muscles, even on birds you can do this, you'll see activity there while you're reading or or or trying to speak

[28:09] out. And so, your speech pathway is now speaking what you're reading. Now, to finish it off, that signal is sent to your auditory pathway so you can

[28:24] >> That's incredible. >> And this is why it's complicated. Oh, and then you got to write, right? Okay, here comes the fourth one. Now, the hand area is next to your speech pathway is got to take that auditory signal or even

[28:38] the adjacent motor signals for speaking and translate it into a visual signal on So, so you're using at least four brain circuits, um which includes the speech production and the speech perception pathways to

[28:52] write. >> Stutter is a um particularly interesting case. What is the current neurobiological understanding of stutter and are uh what's being developed in terms of treatments for stutter?

[29:05] >> Yes, so we actually uh accidentally came across stuttering in songbirds. And we've uh published several papers on this. So, try to figure out the neurobiological basis. The first study we had was a brain area

[29:19] what's the the striatum part of the basal ganglia involved in coordinating movements. When it was damaged in these in this in the speech-like pathway in these birds, what we found is that they started to

[29:34] stutter as the brain region recovered. as the brain region recovered. And unlike humans, they actually recovered after three or four months. And why is that the case? Because bird

[29:46] brains undergoes new neurogenesis in a way that human or mammal brains don't. Uh and it was the new neurons that were coming in into the circuit, uh but not quite, you know, with the right proper activity

[30:01] uh was resulting in this stuttering in these birds. Uh and after it was repaired, not exactly the old song came back as a after repair, but still it recovered a lot better.

[30:13] And it's now known they call this neurogen- neurogenics uh stuttering in humans. Uh with damage to the basal ganglia or some type of disruption to the basal ganglia at a young age also causes stuttering in humans. And even

[30:28] um it's it's often the basal ganglia uh that's disrupted than some other brain circuit. And we think the speech part of the basal ganglia. >> Can adults who maintain a stutter from

[30:42] childhood uh repair that stutter? >> There are ways to overcome the stuttering through um through uh you know, behavioral therapy. Uh and I think all of the uh tools out there

[30:57] integration. Uh controlling what you hear with what you output in a of thoughtful, controlled way helps reduce the >> Texting is a very, very interesting evolution of

[31:14] language. I wonder sometimes whether or not we are getting less proficient at not we are getting less proficient at speech because we are not required to write and think in complete sentences. >> Mhm.

[31:27] language? Are we getting better at speaking, worse at speaking, and what do you think the role of things like texting and tweeting and shorthand communication, hashtagging? Uh what's that doing to the way that our

[31:40] >> Uh texting actually has allowed for more rapid communication amongst people. It's more like a use it or lose it kind of a uh uh

[31:52] uh thing with the brain. The more you use a particular brain region or muscle. Uh the more you exercise it, the more and the more space it takes, and the

[32:05] more you you lose something else. So, I think texting is not decreasing the speech powers, or the intellectual powers of speech. It's converting it and

[32:17] using it a lot in a different way. In a way that may not be as rich in in regular writing because uh you can only communicate so much nuance you can only communicate so much nuance in short term writing. But, um whatever

[32:31] that it whatever is being done, you got people texting hours and hours and hours on the phone. So, whatever your thumb circuit is going to get pretty big, actually. >> For those listening who are interested

[32:44] in getting better at speaking and understanding languages, are there any tools that you recommend? Should kids learn how to read hard books and simple adults learn how to do that? Everyone wants to know how to keep their brain

[32:59] working better, so to speak, but also I think people want to be able to speak understand well. >> Yeah. What I've discovered personally, right, is that So, when I switched from pursuing a career in science from a

[33:14] career in dance, I thought one day I would stop dancing. Um but I haven't because it I find it fulfilling for me. And there've been periods of time like during the pandemic where I slowed down on dancing and so forth. Um And And when

[33:29] there parts of your body where your muscle tone decreases a little bit in some way, and or you could start to gain weight, or I somehow don't gain weight my dance, if that's that that's meaningful to your audience. But what I

[33:43] found is in science, we like to think of a separation between movement and action And there is a separation between between perception and production. Cognition being perception, production being movement, right? But if the speech

[33:59] pathway is next to the movement pathways, what I discover is by dancing, it is helping me think. It is helping keeping my brain fresh. It's not just moving my muscles. I'm moving the or using the the

[34:13] circuitry in my brain to do control a whole big body. You need a lot of brain tissue to do that. And so, I argue, if you want to cognitively intact into your old age, you better be

[34:27] And you better be doing it consistently, whatever it's dancing, walking, running, and also practicing speech, oratory speech and so forth, or singing, is controlling the brain circuits that are moving your facial musculature, and

[34:42] it's going to keep your cognitive circuits also in tune. And I'm I'm experience. >> This has been an incredible conversation and opportunity for me to learn. And I'm I know I speak for a tremendous number

[34:55] of people when I I just really want to say thank you for joining us today. You are incredibly busy. It's clear from your description of your science and involved in a huge number of things. Um very busy. So, thank you for taking

[35:08] the time to speak to all of us. Thank you for the work that you're >> Thank you for inviting me here to get the word out to the community of what's going on in the science world. >> Well, we're honored and very grateful to

[35:20] >> Well, we're honored and very grateful to you, Eric. Thank you. Love you.